Automatic fuel control



May 14, 1946.

D. S. HERSEY AUTOMATIC FUEL ICONTROL Filed Oct. 22, 1941 Patented May14,1946

AUTOMATIC FUEL CONTROL Donald S. Hersey, West Hartford, Conn.,assignorto United Aircraft Corporation, East Hartford, Conn., acorporation of Delaware Application October 22, 1941, Serial No. 416,068

16 claims. (o1. 12s-1840 This invention relates to improvements in fuelsupplying andfuel regulating apparatus for anv internal-combustionengine and has particular reference to such an apparatus for suplying tosuch an engine a quantity Of fuel metered in proportion to the massquantity of air flowing through the engine air intake per unit of time.An object of the invention resides in the provision of improved andsimplified mechanism for determining the mass rate iiow of engine intakeair and adjusting the engine fuel-supply means in accordance withvariations in the mass rate ilow of intake air as determined.

A still further object resides in the provision Of an improved apparatusfor continuously sam# pling the air in the engine intake system betweenthe engine throttle and the engine cylinders and determining the densityof such intake air and applying to such density determination acorrection factor to compensate for variation in the volumetricefficiency of the engine at different engine speeds, and in theprovision of engine fuel supply means responsive to the speed of thevengine and the compensated density determinations of said densitydetermining device for supplyingv to said engine a quantity of fuelmetered in proportion to the mass rate flow of engine intake air.

Other objects and advantages lwill be more particularly pointed outhereinafter or will become apparent as the description proceeds.

In the accompanying drawing, in which like referencenumerals are used todesignate similar parts throughout, there is illustrated a suitablemechanical embodiment for the purpose of disclosing the invention. Thedrawing, however. is for the purpose oi' illustration only and is not tobe takenas limiting or restricting the invention, since it will beapparent to those lskilled in the art that various changes in theillustrated embodimentmay lbe resorted to without in any way exceedingthe scope of the invention.

In the drawing, the single figure is a diagrammatic illustration of anengine fuel supplying and metering apparatus constructed according vtothe invention. certain parts being shown in f section to betterillustrate the construction thereoi'.

parts have been illustrated for the purpose of disclosing the invention,it is to be understoolti that the invention is in no way limited to theparticular type of engine so illustrated and hereinabove described butthat the improved fuel metering apparatus may be applied to variousforms of internal-combustion engines.

Adjacent to the engine air intake there is provided a casing 26enclosing two,chambers 28 and 30 separated by a partition 32 throughwhich extend two apertures o r orices 34 and 36. The chamber 28 isconnected to some portion of the engine intake system between thethrottle and the engine cylinders, such as the diffuser chamber I8, by aIconduit 38 and the chamber 30 is coneoted to the engine air intakesystem through the conduit 40.

While the conduits 38 and 40 are shown connected with the diffuserchamber I8 they may,

if desired, be connected with 'some other part of the intake system,such as the air intake duct 22 as indicated by the blanked Offconnections 42 and 44. y v

Intake air is forced through the casing 26 from one of the ducts 38 or40, 'to the other, by

suitable means such as the positive displacement fluid pump 46 driven bythe constant-speed electric motor 48.

With this arrangement, the pump 46 will force 30 a constant volumetricquantity of air through` the casing 26 and through the orifice apertures34 and 36. With aperture 36 closed the pressure drop across aperture 34from one of the chambers 28 or 30 to the other chamber will con- 35stitute at all times a direct measurement of the density of the air inthe engine intake system at the point where ducts 38 and 40 connect tothe system.

'I'he pressure drop between the chambers 28 40 and 30 is applied to apneumatic device, generally indicated at 5I), through the conduits 52and 54 and this pneumatic device operates a valve 68 which controls aservo-motor, generally indir cated at 58, which in turn regulates thestroke or. 4" capacity of a fuel pump,^generally indicated at 80, whichsupplies fuell to an engine fuel injection device such as the injectionnozzle, generally indicated at 62, of some form well known to Referringto the drawing in detail, the nu- 50 the art, which nozzle may-be'inserted in chammeral I0 generally indicates an internal-com bustionengine having one or more cylinders as indicated at I2 mounted upon aorankcase I4 and supplied with combustible mixture through ber 22.

The pump is driven in some definite proportion to engine speed bysuitable means such as the drive shafts 84 and 86 and the gear connecanindividual intake pipe I8 leading from a 55 tion 68.

supercharger diffuser lchamber I8 into which intake air or combustiblemixture is forced by a supercharger impeller 28 from an air intakeconduit 22 provided with a throttle 24.

While a particular arrangement of` engine 6 If'engine volumetriceiiiciency remained a iixed y,

found to .be necessary for the reason that, volumetric efficiency of theengine changes due to variations in engine speed, therefore, the productof intake air density, engine displacement and engine speed is notnecessarily an adequate measurement; of the mass ow rate of engineintake air, as engine volumetric efficiency is an added factor variablyaffecting the mass flow rate. Also it is found desirable to change thefuel mixture ratio at both ends of the engine speed range to provide asomewhat richer mixture for cooling the engine to some extent andpreventing detonation at the highe speed end of the range, and forinsuring proper ignition of the fuel mixture at the low speed end of theengine speed range,

Compensation for the change in volumetric efficiency and in the fuelmixture at the upper end of the engine speed range is accomplished bythe provision of the second orifice 36, the area of which is controlledby a tapered plug 'I0 actuated by a governor 12 driven from the engineby suitable means, such as the shaft 64 and the gear connections 14 and1G. The governor` 12 may be a conventional type of centrifugal governorhaving centrifugal weights 'I8 acting against the force of a compressionspring 80.

The operation of this compensating mechanism is to increase the areay ofthe orce 36 at the upper end of the engine speed range. This permits afreer flow of air between the chambers 28 and 30 with a consequent dropin the .pressure differential between these chambers. This drop inpressure differential has the same effect on the fuel regulatingmechanism as would be accomplished by a decrease in specific density ofthe engine intake air and will result in a decrease in the amount offuel supplied to the engine to compensate for the somewhat smallerweight OW f intake air to the engine. occasioned by the above mentioneddecrease in volumetric efliciency at the upper end of the engine speedrange. The shape of the plug 'lll also may be so designed, that thedeci-casein amount of fuel supplied will not be as much as would benecessary to completely compensate for the decrease in volumetricemciency so that a somewhat richer fuel mixture will .be supplied to theengine at the upper end of the speed range thus providing an economizeraction which will protect the engine at high speeds but will not resultin excessive use of fuel ,in the intermediate portion of the enginespeed range. The shape of plug lllv may also be such as to provide aricher mixture at low engine speeds for insuring proper ignition, asstated above.

A manually operated mixture controll may be supplied by providing ableed line 82 connected between the conduits 52 and 54 and a valve 84 inthe bleed line controlled tby suitable means such as the link 86 whichmay be connected to an independent manual control.

The pneumatic device 58 and the servo-motor 58 may be of some formalready known to the art or may be specially designed for thisparticular application and are not necessarily restricted to theparticular arrangement illustrated in the accompanying drawing. In theAillustrated arrangement, however, the pneumatic device comprises ahollow casing 83 divided into two sub stantially equal chambers by aflexible transverse partition or diaphragm 90 secured at ,its center tothe intermediate portion of a valve shaft 82. At each end of the casingthe valve shaft 92 is sealed to the casing by respective flexiblediaphragms 94 and SS and at one end this shaft carries the valve member56 which cooperates y with a valve seat provided at the end of apressure fluid conduit 98. The valve is contained in a casing |00 fromwhich a drain line |02 leads to a suitable sump or reservoir from whichthe fluid may be drawn by a pressure creating device, such as the enginelubricating oil pump, and returned through a pressure conduit |04 to thetube 98. At its end opposite the valve 5B the shaft 92 may be connectedwith a dash-pot comprising a piston |06 reciprocable in a closedcylinder |08 provided with restricted openings, as indicated at ||0 and||2 respectively at opposite sides of the piston. 'Ihe purpose of thisdash-pot is to control the rate of change of the capacity of the -pump60 under conditions of rapid opening and closing of the engine throttle.

The servo-motor 58 is connected to the end of the tube 98 opposite thevalve 56 and comprises a cylinder ||4 connected at one end with the tube98 and containing a piston ||6 connected through a piston rod ||8 withthe displacement adjusting element |20 of the variable displacement fuelpump 60. A coiled compression spring |22 urges the piston l I6 in a pumpcapacity decreasing direction opposed by the pressure fluid in the tube98. A flxed restriction |24` is provided in the pressure line |04 sothat the valve 56 may accurately control the fluid pressure in the tube98 by adjusting the opening at the valve end of the tube.

When the bleed valve 84 is opened the bleed between the conduits 52 and54 has the effect of reducing the pressure differential between -theVchambers 28 and A3|) as determined byithe fluid now created by the pumpand on the opposite sides of the diaphragm 90. This decrease in theeffective pressure differential will permit the action of the spring |22to decrease the output capacity of the pump 60 and will result in adecreased quantity of fuel being supplied to the engine intake air tosomewhatl lean the fuel mixture.

With the above described apparatus the fuel supplied to the engine willbe accurately metered in proportion to the mass flow rate of the engineintake air and in addition compensation will be made at the oppositeends of the engine speed l range to somewhat richen the mixture forimproved operation' and protection of the engine without permitting themixture to become excessively rich at the upper end of the Speed rangebecause of the change in volumetric eiciency of the4 engine at this endof the range.

While a suitable mechanical embodiment has been hereinabove describedand illustrated in the accompanying drawing for the vpurpose of dis.

closing the invention, it is to be understood that the invention is notlimited to the particular embodiment so illustrated and described, butthat such changes in the size, shape and arrangements of the Ivariousparts may be resorted to as come within the scope .of the sub-joinedclaims.

Reference is made-to my copending applications Serial Nos'. 311,153 (ledDecember 27, 1939), 370,160 (filed December 14,- 1940), 334,393 (led May10, 1940), and 417,266- (flled October 3l, 1941), which show and claimsubject matter shown but not claimed in the application. Having nowdescribed the invention so that others skilled in the art may clearlyunderstand the same, what it is desired to secure by Letters Patent isas follows:

` 1. A charge forming device for an internalcombustion engine having anair intake system and a fuel supply means driven at a fixed ratio toengine speed and having a controllable displacement per operating cyclecomprising; a fluid conduit connected at both ends with said air intakesystem, a pump in said conduit having a `constant volumetricdisplacement per operating cycle, constant speed means for driving saidpump, a restriction in said conduit, and means pneumatically connectedwith said conduitat opposite sides of .said restriction and operated fbyvariations in the pressure diil'erentialv across said restriction tovary the displacement of said fuel supply' means. f

2.. A charge forming device for an internalcombustion engine having anair intake system and a fuel supply means driven at a ilxedl ratio toengine speed and having a controllable displacement per operating cyclecomprising, a fluid conduit connected at both ends with said air lintake system, a pump in said conduit having a vconstant volumetricdisplacement per operating cycle, constant'speed means i'or driving saidpump, a restriction in said conduit, and means pneumatically connectedwith said conduit at opposite sides of said restriction and operated byl variations in the pressure diiferentia1 across said restrictionto'vary the displacement of said fuel supply means `and speed responsivemeans i'or varying said restriction to compensate the variations in thepressure differential across said restriction for variations in therelation of the volumetric elcien'cy of said engine `to engine speed.

3. A charge-forming device for an internalcombustion engine having anair intake system variable displacement pump arranged .to discharge intosaid stream for adding said liquid to al .gas and driven at said speedproportional to the volumetric flow rate of said gas, means forcontinuously sampling said gas and establishing' across a restriction apressure differential proportional to the density of said gas, and meansactuated by variations in said gas pressure differential for varying thedisplacement of said liquid pump in accordance with variations in saidgas pressure differential, said gas sampling device comprising a casing,ka partition dividing said casing into two chambers, means connectingeach of said chambers with said stream of gas, a pump having a constantdisplacement for each operating cycle disposed in one of said connectingmeans, constant speed means driving said pump;

and a constant area orifice in the partition between said chambers. l

6. Apparatus for adding toa stream of gas a quantity of liquidsuilicient to create a mixture in which the weight of liquid in a unitvolume of gas and a `fuel supply means driven at a ixed ratio to enginespeed and having a controllable displacement per operating cyclecomprising, a fluid conduit connected at both ends with said intakelsystem, a pump having a constant displacement per operating cycle insaid conduit for forcing a stream of sample intake air therethrough,constant speed means for driving said pump, a res triction, in saidconduit comprising a constant area orifice and a variable area orifice,means responsive to engine speed regulating the area of said variablearea orifice to compensate the air pressure drop kacross saidrestriction for change in engine volumetric'efiiciency with a change inengine speed, and means connected with said conduit at opposite sides ofsaid restriction and ac- .uatedby'variationsin the air pressure dropacross said restriction to vary the displacement of said fuel supplymeans.

4. Apparatusfor adding to a stream lof gas a quantity of liquidsufficient to create a mixture in which the weight of liquid in a unitvolume of gas bears a definite predetermined ratio to the weight of gasin said unit volume comprising, a variable displacement pump arranged todischarge into said stream for adding said liquid to said gas andoperated at a speed proportional to the volul metric iiow rate of saidgas, means for continuously sampling said gas, said gas sampling devicecomprising a conduit having its inlet .end in contact with said streamof gas, a pump in -said conduit having a constant displacement peoperating cycle, constant speed means for driving said pump, and arestriction in said conduit, said pump establishing acrossvsaidrestriction a pressure diilerential proportional lto the density of saidgas, and means actuated by variations in .said gas pressure differentialfor varying' the displacement of said liquid pump. y

5. Apparatus `for adding to a. streamof gas a quantity of liquidsufficient to create a mixture bears a denite predetermined ratio to theweight of gas in said unit volume comprising, a variable displacementpump driven at a speed proportional to the volumetric flow rate of saidgas arranged to discharge into said stream for adding said liquid tosaid gas. means for continuously sampling said gas and establishingacross a re' striction a pressure differential proportional to thedensity of said gas, and means actuated by variations in said gaspressurediiferential for varying the displacement of said liquid pump inaccordance with variations in said gas pressure differential, said gassampling device comprising a casing, a partition dividing said casinginto two chambers, means connecting each of said chambers with saidstream of gas, a Pump having a constant displacement for each operatingvcycle disposed in one of said connecting means, constant speed meansdriving said pump, and a constant area orice and a variable' areaorifice in the partition between said chambers.

7. Apparatus for adding to a stream of gas i a quantity of liquidsufficient to create a mixture in which the weight of liquid in a unitvolume of gas bears definite predetermined ratio to the weight of gas insaid unit volume comprising, a

- comprising a conduit, a restriction in said conduit, a pump having aconstant displacement for each operating cycle disposed in said conduitproducing said pressure differential across said restriction, constantspeed meansv driving said pump, and a constant area orifice and avariable varea orifice constituting said restriction, and speed in whichthe weight of liquid in' a unit volume of gas bears a denitepredetermined ratio to the responsive `means for varying the area ofsaid variable area orifice.

8. Apparatus-for adding to a stream of .gas a quantity o! liquidsuiiicient to create a mixture in which the'weight of liquid in a unitvolume of gas bears a, deiinlte predetermined ratio to the weight or gasin. said unit volume comprising, a variable displacement liquid pumpdriven at a weight of gas in said unit volume comprising, a l

v liquid pump in accordance gas pressure drop across said restrictionthrough.

vflow rate' of said gas and arranged to discharge into said gas, meansfor continuously sampling s aid gas and establishing across arestriction a pressure differential proportional to the density of saidgas, and means actuated by variations in said gas pressure differentialfor varying the displacement of said liquid pump in accordance withvariations in said gas pressure diiferential, said liquid pumpdisplacement varying means comprising, a hydraulic motor operativelyconnected with the displacement varying element of said pump. a valvefor controlling said hydraulic motor and a pneumatic motoroperativelylconnected with said valve and pneumatically connected withsaid gas sampling device at opposite sides of said restriction.

9. Apparatus for adding to a stream of gas a quantity of 'liquidsufficient to create a mixture in which the weight of liquid in a unitvolume of gas bears a denite predetermined ratio to the weight of gasinfsaid unit volume comprising, a duct for said gas, a constant speedconstant displacement pump pneumatically connected with said duct for.

continuouslywithdrawing a sample quantity of gas therefrom, arestriction in the connection between said pump and said duct forestablishing in said connection a pressure differential proportional tothe density of the gas, a variable speed adjustable ldisplacement liquidpump connected at its intake side with a supply of liquid and at itsoutlet side with an injecting device adjacent said gas stream, a.hydraulically actuated variable volume mechanism operatively connectedwith said liquid pump for adjusting the displacement l thereof, and apneumatically actuated. mechanism connected to s'aid'pump connectionacross said restriction and operatively connected with saidhydraulically actuated mechanism to adjust the displacement of saidliquid pump in accordance with variations in the gas pressure dropacross said restriction through the intermediacy of said hydraulicallyactuated mechanism.

10. lApparatus for adding to a stream ofV gas a quantity of liquidsufficient to create a mixture in which the weight of liquid in a unitvolume of the capacity varying element of said liquid pump, a'springurging said .piston in a direction to decrease the capacity of saidpump, a fluid pressure line having a restriction therein connected .tosaid cylinder in a manner to apply fluid pressure to said piston toincrease the capacity of said fluid pump, and a bleed valve in saidfluid line operatively'connected with said pneumatically actuatedmechanism to control the fluid pressure applied to said piston.

11. Apparatus for adding to a stream of -gas a quantity of liquidsufficient to create a mixture in which the Weight of liquid in a unitvolume of gas bears a definite predetermined ratio to the weight of gasin said unit volume comprising, a variable displacement pump driven at aspeed substantially proportional to the volumetric flow rate of said gasand arranged to discharge into saidv stream for adding said liquid tosaid gas, means for continuously sampling said gas and establishingacross a restriction a pressure differential proportional to the densityof said gas, andv meansactuated by variations ,in said gas pressuredifferential for varying theI displacement gas y,bears a denitepredetermined ratio tc the weight of gas in said unit volume comprising,a duct for said gas, a constant speed constant displacement pumppneumatically connected with said duct'for continuously withdrawing asamplev quantity-of gas therefrom, a restriction in the connectionbetween said pump and said duct for establishing in said connection apressure .diierential proportional to the density of the gas, a variablespeed adjustable displacement liquid pump connectedv at its intake sidewith a supply v of liquid and at itsoutlet side with an injecting deviceadjacent said gas stream, a hydraulically actuated variable lvolumemechanism operatively connected with said liquid pump for adjusting .the'displacement thereof, and apneumatically actuated mechanism' connectedto said pump connection across said restriction and' operativelyconnectedy with said hydraulically actuated mechanism toadjust thedisplacement of said with variations in the the intermediacy of saidhydraulically actuated mechanism, said hydraulically actuated mechanismcomprising, a cylinder, a piston reciprocable in said cylinder andoperatively connected with of said liquid pump in accordance withvariations in saidV gas pressure differential said liquid pumpdisplacement varying` means comprising, a hydraulic motor deviceincluding a cylinder, a piston reciprocable in said cylinder andoperatively connected with the capacity varying elcment of said liquidpump, a spring urging said piston in a direction to decrease thecapacity oi said pump, a fluid pressure line having a restrictiontherein connected to said cylinder in a manner to apply fluid pressureto said piston in a direction to increase the capacity of said pump, ableed valve in said fluid line for controlling the fluid pressureapplied to said piston, and a pneumatic motor pneumatically connected tosaid gas `sampling device at opposite sides of said restriction andoperatively connected with said valve for controlling the same and adash-pot associated with s ald pneumatic lmotor for stabilizing theoperation thereof.

12. The device of claim 1, including manually operated means for varyingsaid pressure differ'- ential.

l13. The apparatus of claim 1, wherein the variable displacement pumpdischarges into said intake system at a point upstream of said gassampling means.

14. In the combination of claim 1, a supercharger having a diilusersection in said air intake system, said conduit being connected withsaid diffuser section.

15. The device of claim 2, including means to automatically increasethefuel-air weight ratio of said charge at atleast one end of the enginespeed range. A

16. In a charge forming device for an internal combustion engine havingan air intake system and a vvariable delivery fuel pump discharging intosaid intake air, a conduit connected with said air intake system, a pumphaving a constant volumetric displacement per operating cycle in saidconduit, constant speed means for driving said pump, means connectedwith said conduit at opposite sides of said restriction and operated byvaria-l tions inthe pressure striction to vary the delivery of said fuelpump.

DONALD S. HERSEY.

a restriction in said conduit, andv differential across said re

